LONDON, April 16 (Reuters) - Default insurance markets show no obvious concern at the growing risk that Greece will leave the euro zone, suggesting investors can now contemplate a future for the currency union without Athens.

Default probabilities derived from credit default swaps -- seen as the purest gauge of credit risk -- have fallen this year in Italy, Spain and Portugal to around 10 percent, data from Markit show. In Greece, they have topped 80 percent.